In recent years, individual identification technology such as that which gives ID (individual identification numbers) to individual objects and thereby makes information of the objects, such as their history, clear, and makes use of it in production, management, and the like has attracted attention. Among this technology, the development of semiconductor devices which can transmit and receive data contactlessly has been promoted. In particular, semiconductor devices such as these that are beginning to be introduced into businesses, the market, and the like are processor chips (also referred to as RFIDs (radio frequency identification chips), ID tags, IC tags, IC chips, RF tags, wireless tags, electronic tags, and wireless chips) and the like.
Many of these semiconductor devices include a circuit which employs a semiconductor substrate formed of silicon (Si) or the like (hereinafter also referred to as an IC (integrated circuit) chip), and an antenna, and the IC chip includes a memory circuit (hereinafter also referred to as a memory), a control circuit, and the like.
A conventional example of an RFID will be described below with reference to FIG. 16. In FIG. 16, an RFID 700 includes an antenna portion 702 which receives radio waves; a rectifier circuit portion 703 which rectifies output of the antenna portion 702; a regulator circuit 704 which receives output of the rectifier circuit portion 703 and outputs an operating voltage VDD to other circuits; a clock generation circuit 705 which generates clocks; a logic circuit 706 which controls another circuit; a memory 708 which receives output from the logic circuit 706 and performs data writing and reading; and a booster circuit 707 which receives output of the regulator circuit 704 and output of the clock generation circuit 705 and supplies a voltage for writing data to the memory 708.
Besides these circuits, the RFID includes a data modulation/demodulation circuit, a sensor, an interface circuit, and the like, although they are not illustrated.
A reader/writer 701 is a device which writes and reads data to and from the RFID 700 contactlessly from outside.
The antenna portion 702 includes an antenna and a resonant capacitor. The antenna portion 702 takes in a radio wave transmitted from the reader/writer 701, and applies a signal RF_IN obtained at that time to the rectifier circuit portion 703. The rectifier circuit portion 703 includes a diode for rectifying, and a smoothing capacitor. The rectifier circuit portion 703 smoothes RF_IN and generates a voltage VDD0.
The received power which the antenna portion 702 receives is very dependent on the distance of the antenna portion 702 from the reader/writer 701. Therefore, the regulator circuit 704, which puts out a specific output in response to a voltage which is input, is included within the RFID 700 with the aim of preventing the logic circuit and the like from breaking down due to overvoltage which occurs when a chip is placed very near to the reader/writer. The output VDD of the regulator circuit 704 is used as an operating power supply voltage of the logic circuit 706 and as a power supply voltage for when the memory 708 performs a reading operation. When such a structure is employed, the RFID can be operated without a battery.
To perform an operation of writing data to the memory, it is necessary to apply a voltage with a higher potential than that of a voltage used when reading is performed. As a method of generating such a voltage, a method in which the booster circuit is used to boost voltage, based on the output VDD of the regulator circuit, is often used. In FIG. 16, when the output VDD of the regulator circuit 704 and a clock CLK which the clock generation circuit 705 outputs are input to the booster circuit 707, a high power supply potential VDD_HI is obtained as output. Using this VDD_HI, writing is performed to the memory. As an example of using a booster circuit to generate a voltage for writing data to a memory in such an RFID, Reference 1 (Japanese Published Patent Application No. 2006-180073) can be given.